​​In 2012, the evidence of how money was changing American presidential elections came in the form of Newt Gingrich lasting longer than most any pundit imagined he would.

As 2016 approaches, that evidence may be coming in the form of Sen. Rand Paul announcing his bid for the presidency Tuesday. Or Sen. Ted Cruz doing it last month. Or Sen. Marco Rubio (apparently) doing it next week. Or even in Jeb Bush taking his own sweet time.

The GOP field is starting to crowd up – and to grow flush with cash – despite the eagerness of many Republican Party insiders to avoid the kind of bumptious free-for-all that left Mitt Romney battered and looking like he won the GOP nomination by default.

Like Mr. Gingrich, who was a thorn in Mr. Romney’s side for longer than the Republican establishment might have wished, this year’s crop of would-be Republican presidents are filling up on fundraising, making them relatively immune to what the party wants.

Senator Paul has been cultivating millionaire donors, including the Silicon Valley crowd. Senator Rubio has been chatting up the billionaire Koch Brothers. Senator Cruz boldly announced that his goal is to raise as much as $50 million, amid whispers that Jeb Bush could pull in upwards of $100 million by the summer reporting deadline.

What’s new isn’t that lots of candidates are running. It’s that the fund-raising climate can give them higher visibility and potential staying power. With $50 million, Cruz could raise no small ruckus.

As big money rushes into politics in unprecedented sums, the battle lines in the debate over big money seem to be becoming familiar by now. Liberals express outrage over Supreme Court rulings that have opened the door to unlimited sums being spent on politics by groups that can stay virtually anonymous. Conservatives counter that the court merely vindicated free-speech rights sacred since the nation’s founding – including that government can’t tell individuals or groups how much they can spend on speech.

But those interpretations, while important, don’t tell the whole story.

They don’t tell of how the GOP can’t get the hoped-for coronation of an establishment candidate if rogue donors don’t play along. Billionaire casino magnate Sheldon Adelson singlehandedly kept Gingrich in the game in 2012 with a timely $5 million check on the eve of the South Carolina primary. A similar script could play out again in 2016.

Nor do those interpretations hint at the role big money might be playing in the Republican Party’s rightward shift.

Indeed, while all seems comparatively in order on the Democratic front, the 2016 election is offering a glimpse at how Washington’s new era of megamoney is in some ways complicating Republican efforts to retake the White House.

“It’s much more of the Wild West out there,” University of Connecticut political scientist Paul Herrson says of the climate for the nascent 2016 campaign.

The numbers are staggering. By some measures, $2.3 billion was spent on the 2012 presidential race – relatively evenly split between Republicans and Democrats. In 2016, that appears set to surge again – with some speculating the total could even double.

​And a rising share of the total comes from "outside," from groups are keen to influence the race but pledge not to coordinate with a specific candidate or party. Republicans dominated on this front in the 2012 cycle, $720 million to $293 million for Democrats, according to the Center for Responsive Politics, which tracks political spending. But the center's Sheila Krumholz said in an appearance on C-SPAN's "Washington Journal" this week that liberal groups have stepped up their "outside" game, too.

"This is a phenomenon across the political spectrum," she said.

It was this spending that was unleashed by landmark Supreme Court rulings, including Citizens United in 2010. The ability to raise huge sums of money has for years been a prerequisite of any serious presidential contender. Now, candidates can get more and from more places.

Mr. Bush appears to be putting off a presidential announcement as long as possible precisely so that he can legally participate in raising massive amounts of outside cash. That has to stop once a candidate formally announces. (Some legal experts say it should have already stopped, based on Bush’s all-in behavior.) Sizing up such competition, Cruz told The Washington Post that “Jeb Bush will shatter every fundraising record ever set.”

But Cruz vows to keep up. As several Bush groups under the name “Right to Rise” rake in money, the other contenders aren’t walking off the field. They have formed their own super political action committees or similar outside-money groups, and are busy turning to big donors themselves.

“When candidates create their own fundraising committees, separate from party, they are no longer accountable to the diverse elements of a party coalition … but, instead, directly to donors,” Julia Azari, a Marquette University political scientist wrote recently, in a blog post focused on a group allied with Gov. Scott Walker, one of the presumed 2016 Republican candidates.

Is that a problem? Maybe not, some say. Outside money could actually be a positive, giving rise to a broader array of candidates.

But other analysts disagree. Like them or not, the two parties are the nation’s main institutions for distilling competing interests and voices into ideas and candidates that voters can respond to with simple up or down choices on Election Day.

While moneyed interests like business groups and labor unions have always exerted power alongside other activists within the parties, it’s not clear what layering extra money from the outside accomplishes.

Congress’s latest answer has been to add yet more money to the inside. Now, a wealthy couple can give $3 million directly to party committees in a two-year period, a big boost from limits that had been set in the 2002 McCain-Feingold Act, says Robert Maguire of the Center for Responsive Politics.

To be sure, the Republican Party is not being pushed out of the picture.

“Money in American politics has always been necessary but not sufficient” to win the nomination, says Martin Cohen, a political scientist at James Madison University in Harrisonburg, Va.

After all, when Bush made an exploratory visit to New Hampshire, his stops included a meet-and-greet hosted by Fergus Cullen, a former chairman of the state’s Republican Party. While it’s unlikely any candidate will get the nod without succeeding on the fundraising trail, the parties still hold huge sway on the path to winning their own nominations. Romney’s eventual triumph in 2012 showed that.

But big money might be making the GOP’s life more difficult in other ways, too. Though the influences that lead to partisanship are varied, a 2013 study by the Sunlight Foundation, a group that researches money in politics, concluded that the wealthiest donors “may be pulling Republicans to the political right, acting as a force for a more polarized Congress.”

The foundation matched rankings of lawmaker partisanship with data on the share of campaign funding that each lawmaker gets from the largest 31,385 political donors. (That number of donors represents an elite “1 percent of the 1 percent” of the overall US population.)

Whether that is a good thing is largely in the eye of the beholder. Back in the 1950s, the two parties drew scholarly criticism for being too ideologically similar. Public opinion polls now find Americans generally worried about the shortage of compromise in Washington.

But as the Republican Party faces a robust crop of candidates courting the right in 2016, the role of big money in fueling the rightward shift of the party – and financing the candidates who seek to capitalize from it – appears to be coming into clearer focus.